The present invention relates to a system and method for peeling crustaceans.
In, for example, British Patent Specification No. 2,122,871, corresponding to U.S. Pat. No. 4,639,976, the crustaceans are initially subjected to a short duration heating treatment so that the shells and areas jsut inside the shells are heated to a temperature higher than a temperature of interior meat portions of the crustaceans, whereafter, the crustaceans are subject to a rapid pressure drop so that the body liquid just beneath the shell is caused to boil vividly without the liquid in the inside portions of the crustaceans being brought to a boil. By this boiling action in the outer region, a substantial loosening of the shells from the outer surfaces of the meat bodies occurs and immediately after, or in connection with the outer boiling of the crustaceans, the crustaceans are caused to be moved rapidly towards or against a liquid surface, which will show a braking action on the outer shell portions, while the inner meat portions will continue their movement by the associated motion inertia, whereby the shell portions, as loosened, by the boiling, will be widely stripped off the meat bodies.
By virtue of the above described approach the crustaceans may shelled without any traditional and partly destroying mechanical treatment, and it has been found that a complete deshelling is achievable by recirculation of the crustaceans, which have been only partly shelled by the first treatment, as still occurring rests of shells will then be loosened by a renewed local heating of the liquid immediately underneath the shell rests, without the remaining crustaceans being damaged by a renewed very brief surface boiling and a following rapid movement of the animal into a braking liquid surface. In this manner it is possible to remove, for example, an average of some 50% of the shells by a first operation, while in a following operation additionally some 30% of the shells may be removed, and then finally some 15-18% in a third operation, such that the final result after three operations or two recirculations will be a practically acceptable removal of about 98% of the shells from the animals, while during the repeated treatments only very little of the meat product will get lost. Thus, this process exhibits a very high efficiency as compared with conventional mechanical treating of the crustaceans.
The purpose of the present invention is to provide a system and method of the aforementioned type, by which the efficiency or economy may be further improved. It has been found, rather surprisingly, that at least for many types of crustaceans such as shrimp it is possible to achieve a practically acceptable deshelling in only a single operation, when the braking liquid is present on an inclined deflector plate, against which the crustaceans are shot, rather than down into a bath of the liquid. However, there should preferably be used two deflector plates, arranged one after the other, such that the crustaceans after having hit the first plate will continue against the second plate and from there be conveyed for delivery to suitable separation means for the meat and the shells, respectively.
It is important that practically all of the crustaceans should individually hit the deflector plate or plates and not hit the plate members in a thick flow, as in the latter case many crustaceans would just hit each other and thereby be braked too softly to condition an effective deshelling. With the above described method it is possible to operate with a considerable amount of crustaceans per "shot", e.g. 1 kg of shrimps, because the crustaceans, by the firing down into the liquid, will all be subjected to the braking action of the liquid, while in connection with the invention the crustaceans, as mentioned, should be supplied in a thin flow or only few at a time. However, it is still possible to work with a considerable capacity, partly because the crustaceans may be shot against the plate from several supply ports arranged near each other, and partly because the crustaceans may be shot off with short intervals between the single small doses, e.g. at a rate of one dosis per second.
The invention shows the additional advantageous effect that the deshelled crustaceans will only to a limited degree or during a short interval of time need to be present in water, it being well known that the taste qualities of the crustaceans are considerably reduced, the longer the crustaceans are held in water. With the proposed method it is necessary to shoot the crustaceans down into a water bath and thereafter to move them in water to a special separator, in which the entirely deshelled crustaceans are separated, in water, from the shells and from the only partly deshelled crustaceans, and the latter will moreover have to be recirculated at least once through the system, upon their being separated from the loose shells, e.g. by air separation. In connection with the present invention it is sufficient to make use of an air separation for separating the shells from the entirely deshelled crustaceans, i.e. the liquid separator will simply not be required, and it is sufficient to use only a small amount of flow of water for a rapid transfer of the mixture of shells and crustaceans from the vacuum chamber to the air separator or to a conveyor for bringing the product to the air separator, whereby the crustaceans should remain in water for some few seconds only.
Thus, with the method and the system according to the invention is achieved both a high capacity due to the lack of any need of recirculation of the products, a simple design of the apparatus, because the said liquid separator can be avoided, and an improved quality of the products, because they are exposed to water only to a very limited degree.
Further details and advantages of the invention, which is defined more precisely in the appended claims, will appear from the following description with reference to the drawing, in which: